# US 7,611,912 B2 · Underlayer for high performance magnetic tunneling junction MRAM

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- Number: US 7,611,912 B2
- Document ID: US7611912B2
- Status: Granted
- Kind: B2
- Application number: 10/881,445
- Filed: 2004-06-30
- Published: 2006-01-05
- Granted: 2009-11-03
- Earliest claimed: 2004-06-30
- Assignees: Headway Technologies, Inc.
- Inventors: Liubo Hong; Cheng Horng; Mao-Min Chen; Ru-Yin Tong
- Web page: https://patentgrep.com/patent/US7611912B2

## CPC

- H10N 50/01: Manufacture or treatment
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- B82Y 25/00: Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
- B82Y 40/00: Manufacture or treatment of nanostructures
- G01R 33/09: Magnetoresistive devices
- G01R 33/093: {using multilayer structures, e.g. giant magnetoresistance sensors (thin magnetic films H01F10/00)}
- G01R 33/098: {comprising tunnel junctions, e.g. tunnel magnetoresistance sensors}
- G11B 5/3906: {Details related to the use of magnetic thin film layers or to their effects}
- G11B 5/3909: {Arrangements using a magnetic tunnel junction}
- G11C 11/161: {details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell}
- G11C 11/1673: {Reading or sensing circuits or methods}
- H01F 10/30: characterised by the composition of the intermediate layers {, e.g. seed, buffer, template, diffusion preventing, cap layers (H01F10/06 and H01F10/32 take precedence)}
- H01F 10/3254: {the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]}
- H01F 10/3295: {Spin-exchange coupled multilayers wherein the magnetic pinned or free layers are laminated without anti-parallel coupling within the pinned and free layers}
- H01F 41/307: {insulating or semiconductive spacer}
- H10N 50/10: Magnetoresistive devices
- H10N 50/85: Materials of the active region
- H01F 10/3259: {Spin-exchange-coupled multilayers comprising at least a nanooxide layer [NOL], e.g. with a NOL spacer}
- H01F 10/3272: {by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets}
- H10B 61/00: Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- Y10T 428/1114: having tunnel junction effect
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- G11C: STATIC STORES (semiconductor memory devices H10B)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H10B: ELECTRONIC MEMORY DEVICES
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An MRAM structure is disclosed in which the bottom electrode has an amorphous TaN capping layer to consistently provide smooth and dense growth for AFM, pinned, tunnel barrier, and free layers in an overlying MTJ. Unlike a conventional Ta capping layer, TaN is oxidation resistant and has high resistivity to avoid shunting of a sense current caused by redeposition of the capping layer on the sidewalls of the tunnel barrier layer. Alternatively, the α-TaN layer is the seed layer in the MTJ. Furthermore, the seed layer may be a composite layer comprised of a NiCr, NiFe, or NiFeCr layer on the α-TaN layer. An α-TaN capping layer or seed layer can also be used in a TMR read head. An MTJ formed on an α-TaN capping layer has a high MR ratio, high Vb, and a RA similar to results obtained from MTJs based on an optimized Ta capping layer.

## Claims

### Claim 1

A method of forming an MRAM structure on a substrate, comprising:
(a) forming a bottom electrode that is comprised of a seed layer on a substrate, a Ru, Rh, or Ir conductive layer on the seed layer, and an α-TaN capping layer on the conductive layer wherein the capping layer forms a planar film;
(b) forming an MTJ element comprised of a pinned layer/tunnel barrier/free layer stack and having a top surface, bottom surface, and sidewalls, said bottom surface contacts a top surface of said capping layer in the bottom electrode; and
(c) forming a top electrode on the top surface of the MTJ element.

### Claim 2 (depends on 1)

The method of claim 1 wherein the α-TaN capping layer has a thickness of about 50 to 400 Angstroms and a nitrogen content between about 25 and 35 atomic %.

### Claim 3 (depends on 2)

The method of claim 2 wherein said α-TaN capping layer is formed by a reactive sputtering process with a nitrogen containing plasma.